/*
 * Copyright (c) 2013, SRI International
 * All rights reserved.
 * Licensed under the The BSD 3-Clause License;
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 * 
 * http://opensource.org/licenses/BSD-3-Clause
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * 
 * Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 * 
 * Neither the name of the aic-util nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.sri.ai.util.collect;

import java.util.Iterator;
import java.util.NoSuchElementException;

import com.google.common.annotations.Beta;

/**
 * An iterator ranging over a base iterator's range but including only those
 * elements satisfying a condition. The condition is provided by the abstract
 * method {@link include(E)}.
 * 
 * @author braz
 */
@Beta
public abstract class FilterIterator<E> implements Iterator<E> {

	private E next;
	private boolean onNext = false;
	protected Iterator<E> base;
	
	public FilterIterator(Iterator<E> base) {
		this.base = base;
	}

	public abstract boolean include(E element);

	public boolean hasNext() {
		ensureNextIsCalculated();
		return onNext;
	}

	public E next() {
		if ( ! hasNext()) {
			throw new NoSuchElementException();
		}
		onNext = false;
		return next;
	}

	public void remove() {
		base.remove();
	}

	private void ensureNextIsCalculated() {
		if (onNext) {
			return;
		}
		while (base.hasNext()) {
			next = base.next();
			if (include(next)) {
				onNext = true;
				return;
			}
		}		
		onNext = false;
	}
}
